package org.apache.lucene.search.spans;

/**
 * Copyright 2004 The Apache Software Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.io.IOException;

import java.util.Collection;

import org.apache.lucene.index.IndexReader;
import org.apache.lucene.search.Query;
import org.apache.lucene.util.ToStringUtils;

/** Removes matches which overlap with another SpanQuery. */
public class SpanNotQuery extends SpanQuery {
    private SpanQuery include;
    private SpanQuery exclude;

    /** Construct a SpanNotQuery matching spans from <code>include</code> which
     * have no overlap with spans from <code>exclude</code>.*/
    public SpanNotQuery(SpanQuery include, SpanQuery exclude) {
        this.include = include;
        this.exclude = exclude;

        if (!include.getField().equals(exclude.getField()))
            throw new IllegalArgumentException("Clauses must have same field.");
    }

    /** Return the SpanQuery whose matches are filtered. */
    public SpanQuery getInclude() {
        return include;
    }

    /** Return the SpanQuery whose matches must not overlap those returned. */
    public SpanQuery getExclude() {
        return exclude;
    }

    public String getField() {
        return include.getField();
    }

    public Collection getTerms() {
        return include.getTerms();
    }

    public String toString(String field) {
        StringBuffer buffer = new StringBuffer();
        buffer.append("spanNot(");
        buffer.append(include.toString(field));
        buffer.append(", ");
        buffer.append(exclude.toString(field));
        buffer.append(")");
        buffer.append(ToStringUtils.boost(getBoost()));
        return buffer.toString();
    }

    public Spans getSpans(final IndexReader reader) throws IOException {
        return new Spans() {
            private Spans includeSpans = include.getSpans(reader);
            private boolean moreInclude = true;

            private Spans excludeSpans = exclude.getSpans(reader);
            private boolean moreExclude = true;

            public boolean next() throws IOException {
                if (moreInclude) // move to next include
                    moreInclude = includeSpans.next();

                while (moreInclude && moreExclude) {

                    if (includeSpans.doc() > excludeSpans.doc()) // skip exclude
                        moreExclude = excludeSpans.skipTo(includeSpans.doc());

                    while (moreExclude // while exclude is before
                                    && includeSpans.doc() == excludeSpans.doc() && excludeSpans.end() <= includeSpans.start()) {
                        moreExclude = excludeSpans.next(); // increment exclude
                    }

                    if (!moreExclude // if no intersection
                                    || includeSpans.doc() != excludeSpans.doc() || includeSpans.end() <= excludeSpans.start())
                        break; // we found a match

                    moreInclude = includeSpans.next(); // intersected: keep scanning
                }
                return moreInclude;
            }

            public boolean skipTo(int target) throws IOException {
                if (moreInclude) // skip include
                    moreInclude = includeSpans.skipTo(target);

                if (!moreInclude)
                    return false;

                if (moreExclude // skip exclude
                                && includeSpans.doc() > excludeSpans.doc())
                    moreExclude = excludeSpans.skipTo(includeSpans.doc());

                while (moreExclude // while exclude is before
                                && includeSpans.doc() == excludeSpans.doc() && excludeSpans.end() <= includeSpans.start()) {
                    moreExclude = excludeSpans.next(); // increment exclude
                }

                if (!moreExclude // if no intersection
                                || includeSpans.doc() != excludeSpans.doc() || includeSpans.end() <= excludeSpans.start())
                    return true; // we found a match

                return next(); // scan to next match
            }

            public int doc() {
                return includeSpans.doc();
            }

            public int start() {
                return includeSpans.start();
            }

            public int end() {
                return includeSpans.end();
            }

            public String toString() {
                return "spans(" + SpanNotQuery.this.toString() + ")";
            }

        };
    }

    public Query rewrite(IndexReader reader) throws IOException {
        SpanNotQuery clone = null;

        SpanQuery rewrittenInclude = (SpanQuery) include.rewrite(reader);
        if (rewrittenInclude != include) {
            clone = (SpanNotQuery) this.clone();
            clone.include = rewrittenInclude;
        }
        SpanQuery rewrittenExclude = (SpanQuery) exclude.rewrite(reader);
        if (rewrittenExclude != exclude) {
            if (clone == null)
                clone = (SpanNotQuery) this.clone();
            clone.exclude = rewrittenExclude;
        }

        if (clone != null) {
            return clone; // some clauses rewrote
        } else {
            return this; // no clauses rewrote
        }
    }

    /** Returns true iff <code>o</code> is equal to this. */
    public boolean equals(Object o) {
        if (this == o)
            return true;
        if (!(o instanceof SpanNotQuery))
            return false;

        SpanNotQuery other = (SpanNotQuery) o;
        return this.include.equals(other.include) && this.exclude.equals(other.exclude) && this.getBoost() == other.getBoost();
    }

    public int hashCode() {
        int h = include.hashCode();
        h = (h << 1) | (h >>> 31); // rotate left
        h ^= include.hashCode();
        h = (h << 1) | (h >>> 31); // rotate left
        h ^= Float.floatToRawIntBits(getBoost());
        return h;
    }

}
